A fluorocarboxylic acid having an ether bond, for example, 2,3,3,3-tetrafluoro-2-[1,1,2,3,3,3-hexafluoro-2-(trifluoromethoxy)propoxy]-propanoic acid has a solubility in water of about 10% at normal temperature, which is about 50 times of the solubility of perfluorooctanoic acid (PFOA) in water. Therefore, the adsorption rate of general active carbon, for example, general-purpose active carbon for waste water which was conventionally used is 5% or less at normal temperature and pH 7.
It was difficult to highly adsorb the fluorocarboxylic acid having an ether bond, which has high solubility in water, with using the conventional active carbon having a specific surface area of 1,000 m2/g or less. Such adsorption method was associated with problems of cost.    Patent Document 1: JP-A-09-315809